The present invention concerns methods utilizing ion-exchange resin bodies in the treatment of alkali metal solutions to remove undesired chlorate and chloride ions therefrom.
Composite ion exchange resin bodies and their use in separating solutes, at least one of which is ionizable, from solutions thereof, including salt impurities from alkali metal solutions, are known in the art and are often referred to as "snake cage polyelectrolytes". See, for example, U.S. Pat. Nos. 3,078,140, 3,041,292, Canadian Pat. No. 575,049 and the Hatch et al publication entitled "Preparation and Use of Snake-cage Polyelectrolytes", Ind. and Eng. Chem., Vol. 49, pp. 1812-1819, 1957. The '049 Canadian patent teaches that chloride and chlorate ions can be absorbed from solutions containing about 30 to about 50 weight per percent sodium hydroxide to permit recovery of a purified solution. However, it has been discovered that use of the known snake-cage polyelectrolyte resins are not effective in treating certain alkali metal solutions, particularly sodium hydroxide solutions of from about 15 to about 35 weight percent sodium hydroxide, to obtain a purified solution containing acceptably low levels of salt impurities.